This invention relates to biocidal 4,5-dichloro-1,2-dithiol-3-one compositions which are excellent in solubility and stability in storage and easy to handle.
4,5-Dichloro-l,2-dithiol-3-one (hereinafter referred to as dithiol compound) is the compound of the formula (I): ##STR1## in yellow crystalline powders, m.p. 61.degree. C. which has been used as an excellent slime control agent for industrial cooling water, washing water, raw water and power water (Japanese Patent Examined Publication (Kokoku) No. 14294/1977). The dithiol compound, produced in powdery form, is extremely difficult to handle during the production work since it is highly skin-irritant. Besides, such powdery form is very inconvenient in handling the product thereof.
Therefore, it is considered to be advantageous and convenient in workability, safety, storability, transportability and dispersibility in use to make the powders into liquid preparations.
Particularly, it is economic to permit the liquid preparations of these industrial microbicidal compounds to contain the effective ingredient at as high concentration as possible for transportation and storage thereof. Moreover, these liquid preparations are required to have high stability during transportation and storage.
However, the dithiol compound itself is a sparingly water-soluble substance having a solubility in water of below 1%, and thus it cannot be made an aqueous solution of high concentration. Furthermore, the dithiol compound is very unstable in the obtained aqueous solution and susceptible to hydrolysis in a short period of time. Thus, such an aqueous solution cannot be put into practical use.
In the specification of U.S. Pat. No. 4647577, as the research for making a liquid preparation of the dithiol compound, there are disclosed liquid preparations which are obtained by dissolving the dithiol compound in a haloacetic acid ester as the solvent, which is hydrophobic (lipophilic) solvent. However, when 1,2-bis(bromoacetoxy)ethane among the haloacetic acid esters, is used as a solvent, the solubility of the dithiol compound is about 22%. The liquid preparations having such an extent of solubility cannot be regarded as ones of sufficiently high concentration in terms of transportation economy.
In Japanese Patent Examined Publication (Kokoku) No. 23721/1987, there are disclosed liquid preparations which are obtained by dissolving the dithiol compound in a mixed solvent of diethylene glycol monomethyl ether and dimethylformamide. The solubility of the dithiol compound in this solvent is about 67 weight % at 25.degree. C., which is very high and the obtained liquid preparations are pretty sufficient in respect of the solubility of the dithiol compound. However, dimethylformamide is inherently so strong in toxicity that it is problematic to use it in a large amount as a solvent. Also, these liquid preparations are insufficient to storage and stability of the dithiol compound over a long period. Besides, liquid preparations containing the dithiol compound at a high concentration have defects that, when they are exposed to a low temperature in transportation or storage, crystallization occurs followed by the solidification of the whole liquid preparations. These solidified products are so hard that it is difficult to even take them out of the vessel thereof and it is necessary to redissolve them by heating for utilizing. This is highly disadvantageous in work and thermal economy.
On the other hand, U.S. Pat. No. 4,595,679 discloses the use of pyrrolidone compounds such as N-vinyl-2-pyrrolidone, N-methyl-2-pyrrolidone and 2-pyrrolidone, as an emulsifying agent or a solvent for an insecticidal composition, and that the use of pyrrolidone compound increases the penetration of the insecticide into the body of the insect to provide enhanced insect knockdown.